async function async1() {
  await async2();
  console.log('async1');
}
async function async2() {
  await async3();
  console.log('async2');
}
async function async3() {
  console.log('async3');
}
console.log('script start');
async1();
new Promise(function (resolve) {
  resolve();
}).then(function () {
  console.log('promise');
});
console.log('script end');
